Q. A guy at the gym told me that more than 8 reps won’t help me build muscle. Should I always do less than 8 reps?
A. It’s true that lower repetitions (6-12) will help you build size and strength. Higher repetitions (12-20) will build muscular endurance. However, there is nothing magical about the number eight.
Studies show that you can build muscle with a range of different repetitions. For example, a recent trial tested the effects of three different repetition ranges. The first programme involved 3-5 repetitions for four sets. Programme two used 9-11 repetitions for three sets. Two sets of high repetitions (20-28) were used in programme three. Gains in strength were greatest in the low repetition group. However, the major muscle fibres grew larger and thicker in both the low- and medium-repetition groups. There were no big changes in fibre size in the high-repetition group.
In short, to build muscle strength and size, keep your repetitions between 6-12. To gain strength, you can also occasionally include very heavy weights and low repetitions.